What happens to the size of the circles over time? What does this represent? They grow larger. This represents the population growing.

Generally, which direction do the circles move on the y-axis – that is, what happens to average life expectancy over time? Where and why do we see counter-examples? Life expectancy generally increases over time. Russia, Spanish Flu.

Which direction do the circles move on the x-axis – that is, what happens to GDP over time? Where and why do we see outlier examples? In general, it increases. 1920's, Kuwait

Do you think that GDP, or wealth, is related to life expectancy? If so, how? Yes

What other questions might students explore using this tool? Looking at historical events. Change parameters for science/public health. Look at particular countries.